1. ¹Department of Biology, University of North Carolina at Charlotte, Charlotte, NC, USA
2. ²Faculty of Life Sciences, The University of Manchester, Manchester, UK
3. ³Department of Anatomy and Neurobiology, Washington University School of Medicine, St Louis, MO, USA

Correspondence: Dr LJ Leamy, Department of Biology, University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, NC 28223, USA. E-mail: ljleamy@uncc.edu

Received 9 May 2008; Revised 1 July 2008; Accepted 11 July 2008; Published online 6 August 2008.

Abstract

Genomic imprinting refers to the pattern of monoallelic parent-of-origin-dependent gene expression where one of the two alleles at a locus is expressed and the other silenced. Although some genes in mice are known to be imprinted, the true scope of imprinting and its impact on the genetic architecture of a wide range of morphometric traits is mostly unknown. We therefore searched for quantitative trait loci (QTL) exhibiting imprinting effects on mandible size and shape traits in a large F₃ population of mice originating from an intercross of the LG/J (Large) and SM/J (Small) inbred strains. We discovered a total of 51 QTL affecting mandible size and shape, 6 of which exhibited differences between reciprocal heterozygotes, the usual signature of imprinting effects. However, our analysis showed that only one of these QTL (affecting mandible size) exhibited a pattern consistent with true imprinting effects, whereas reciprocal heterozygote differences in the other five all were due to maternal genetic effects. We concluded that genomic imprinting has a negligible effect on these specific morphometric traits, and that maternal genetic effects may account for many of the previously reported instances of apparent genomic imprinting.